It is always a good idea to keep the selection statements small. You can
always make a large selection and gradually make it smaller. In the
previous case I think you would need an "and" before the last segment.

As said before anything is possible with VMD especially when you couple it
with the command line. One thing to keep in mind is that you could use
Graphic//Representation//selection to try out these commands. By entering
combinations in the selection tap and clicking "create rep" would update
the visualization window or give an error like you just said "can not parse
selection".

Do not that in the selection tab you don't have to say

set sel1 [atomselect $mol {...

You will only put the selection statement which is in the curly braces in
my previous message or use Norman's method or make your own new one. This
would help you troubleshoot your selection statement rapidly and hence not
be dependant on answers here.